1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method, and in particular, to generation of a color separation table used in converting an image signal into a signal for the amount of a colorant, such as ink and toner.
2. Description of the Related Art
FIG. 11 is a flowchart showing an example of generation of a color separation table. First, grid-point data is determined on the basis of calorimetric values of a patch (step S11-1). Then, grid-point data on grid points lying on the lines connecting eight vertexes of the color separation table, i.e., six lines of W-C, M, Y, R, G, and B, six lines of C, M, Y, R, G, and B-K, and other lines of M-R, R-Y, Y-G, G-C, M-B, B-C, W-K, wherein W denotes white, C denotes cyan, M denotes magenta, Y denotes yellow, R denotes red, G denotes green, B denotes blue, K denotes black, is determined (step S11-2). Grid-point data of grid points other than the grid points determined in S11-2 is determined by interpolation processing (step S11-3). After the interpolation processing, the grid-point data is subjected to smoothing processing to reduce discontinuity at the boundaries of interpolation areas and other undesired states (step S11-4). Then, the grid-point data of the entire smoothed table is compared with the maximum allowable amount of discharge for a print medium, and it is determined whether a grid point that has grid-point data exceeding the maximum allowable amount of discharge is present or not. If such a grid point is present, the amount of discharge regarding the grid point is corrected (step S11-5).
For the sake of improving recording image quality, different types of recording media for use in recording are selectively used.
In the case where multiple types of recording media are selectively used, grid-point data for respective recording media is determined on the basis of adhesion characteristics of colorants to the recoding media (e.g., paper). For example, when ink is used as the colorant, grid-point data is determined so as to control the amount of the colorant on the basis of absorbency of a recording medium to the ink. In other words, the maximum allowable amount of ink that can be absorbed in the recording medium per a predetermined area is obtained in advance, and the amount of the colorant for each color is corrected so as not to exceed the maximum allowable amount.
FIG. 12 illustrates an example of color separation on the W-K line for a first recording medium before the amount of discharge is corrected. The horizontal axis represents the value of a grid point, and the vertical axis represents the value of a signal. Aside from the value of a signal, the vertical axis represents the maximum allowable amount of discharge which is, in this example, 160. Since the total amount of ink discharge exceeds the maximum allowable amount of discharge, recording on the recording medium without correcting the amount of ink discharge results in an overflow of ink.
FIG. 13 illustrates an example of the color separation on the W-K line shown in FIG. 12 after the amount of discharge is corrected. Since the amount of discharge has been corrected, the total amount of discharge does not exceed the maximum allowable amount of discharge and the recording medium can absorb ink without causing the ink to overflow.
FIG. 14 illustrates an example of color separation on the W-K line for a second recording medium before the amount of discharge is corrected.
FIG. 15 illustrates an example of the color separation on the W-K line shown in FIG. 14 after the amount of discharge is corrected. The maximum allowable amount of discharge for the second recording medium is 190 which is larger than that for the first recording medium shown in FIGS. 12 and 13.
However, generation of a color separation table for each type of a recording medium for use in recording increases the design workload. The design workload significantly increases with an increase in the number of types of recording media.
Even when color separation tables corresponding to different types of recording media are designed, the tables are often required to be designed in the same period of time as in designing of a color separation table corresponding to a single type of recording medium. Therefore, it is difficult to allocate time among the generations of the color separation tables corresponding to the different types of recording media.